Various synthetic roof and wall coverings, such as those formed of elongated thermoplastic panels that are nailed to a wall or roof support surface in horizontal courses or rows in partially overlapping relation to each other so as to provide a substantially water resistant, protective layer over the support surface, are known today. Such panels, which usually are identically molded, are commonly formed with a plurality of rows of simulated building elements, such as shake shingles. Because the panels are identically molded, a panel-to-panel identity can be easily noticed if the panels are not carefully installed. Leakage problems between adjoining panels can also occur under these circumstances.
To facilitate installation, such panels typically are nailed to the wall or support surface along an upper horizontal nailing flange with the lower marginal edge region overlapping the panel in the course immediately below and with one side marginal edge region overlapping the laterally spaced adjacent panel. While various means have been proposed for interlocking the overlapping portions of adjacent panels to provide a water seal therebetween and to minimize the noticeability of the junctions between panels, such interlocks often have been cumbersome to engage during installation and frequently have been ineffective in establishing and maintaining sealed engagements between panels, particularly when the panels are mounted on irregular surfaces or are exposed to extreme weather conditions.
More specifically, since such panels are relatively large in size, it is necessary that they be firmly positioned upon the wall or roof surface upon which they are mounted and that they be reliably interlocked along both upper and side marginal edge regions in order to prevent the adjoining edges of the panels from being noticeable and in order to provide a reliable seal between such edges. Because the panels are exposed to relatively wide temperature variations, however, they can experience significant expansion and contraction after installation. Such thermal expansion and contraction can disrupt seals between the panels and detract from the finished appearance of the wall covering if proper accommodation is not made.
While it is desirable to interlock both the horizontal and vertical sides of such panels with adjacent panels, heretofore it has been difficult to provide for reliable interlocks while still permitting adequate expansion and contraction of the installed panels. For example, with respect to the horizontal sides, proposals have been made for locating the lower marginal edge region of an overlapping panel in predetermined relation to the underlying interlock at a precise location so as to permit both expansion and contraction of the panels. However, this heretofore has been a relatively tedious installation step. Proposals to assist the installer of the panels in locating the overlapping marginal edge region at the precise desired location also have not been entirely reliable, or often are ignored by hasty installers, or are cumbersome.
Interlocking the side marginal edge regions of such panels also have presented problems. Since the panels are relatively long, engaging or locking the peripheral edges of the panels can create undesirable bowing of the panels during installation and during use when the panels undergo thermal expansion or contraction. In addition to bowing, if proper accommodations are not made, expansion or contraction can also fracture the flanges which interlock the panels together. Moreover, when one or more of these flanges are so fractured, the remaining flanges often are insufficient to adequately retain or support the panel in the mounted position, and, in the long term, dis-orientation of the panel, leakage, and the subsequent need for repair and replacement can result.